WorldCat Identities

Begaud, Xavier

Overview
Works: 50 works in 77 publications in 2 languages and 576 library holdings
Genres: Conference papers and proceedings 
Roles: Thesis advisor, Other, Editor, Opponent, Author, Contributor, Publishing director
Publication Timeline
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Most widely held works by Xavier Begaud
Ultra-wide band antennas by Xavier Begaud( )

16 editions published between 2010 and 2013 in 3 languages and held by 510 WorldCat member libraries worldwide

Ultra Wide Band Technology (UWB) has reached a level of maturity that allows us to offer wireless links with either high or low data rates. These wireless links are frequently associated with a location capability for which ultimate accuracy varies with the inverse of the frequency bandwidth. Using time or frequency domain waveforms, they are currently the subject of international standards facilitating their commercial implementation. Drawing up a complete state of the art, Ultra Wide Band Antennas is aimed at students, engineers and researchers and presents a summary of internationally recog
Optimisation d'antennes et de circuits à l'aide des métamatériaux by Davi Bibiano Brito( Book )

3 editions published in 2010 in English and held by 3 WorldCat member libraries worldwide

Metamaterials have attracted a great amount of attention in recent years mostly due to their exquisite electromagnetic properties. These materials are artificial structures that exhibit characteristics not found in nature. It is possible to obtain a metamaterial by combining artificial structures periodically. We investigated the unique properties of Split Ring Resonators, High impedance Surfaces and Frequency Selective Surfaces and composite metamaterials. We have successfully demonstrated the practical use of these structures in antennas and circuits. We experimentally confirmed that composite metamaterials can improve the performance of the structures considered in this thesis, at the frequencies where electromagnetic band gap transmission takes place
Contribution à l'étude du couplage entre antennes, application à la compatibilité électromagnétique et à la conception d'antennes et de réseaux d'antennes by Alireza Kazemipour( Book )

2 editions published in 2002 in French and held by 2 WorldCat member libraries worldwide

Analysis and optimization of a wideband metamaterial absorber made of composite materials by Olivier Rance( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

Analyse d'antennes et de réseaux d'antennes large bande et bipolarisation par une méthode d'éléments finis de surface by Xavier Begaud( Book )

2 editions published in 1996 in French and held by 2 WorldCat member libraries worldwide

L'objectif principal de ce travail est la conception et l'analyse d'antennes à bande passante de l'octave et multioctaves, bipolarisation, isolées ou dans un environnement réseau, à l'aide d'un outil performant de modélisation par éléments finis de surface. Cette étude s'inscrit dans un thème d'intérêt général: l'obtention de réseaux large ou très large bande, bipolarisation, multifonctions, destines par exemple à diminuer le nombre d'aériens embarques sur les avions. La conception de tels réseaux nécessite la connaissance précise de l'ensemble des caractéristiques de rayonnement de chaque antenne. L'outil de modélisation par éléments finis de surface permet de répondre à ce besoin et fournit un ensemble de résultats nécessaires à la caractérisation polarimétrie de ces réseaux. Les principaux aspects novateurs de ce travail se situent au niveau de: la conception et l'optimisation d'une antenne fente multi octaves et bipolarisation a faible impédance d'entrée. Cette antenne a fait l'objet d'un dépôt de brevet. La mise au point d'une méthode simple et compatible avec la modélisation par éléments finis de surface, de la prise en compte des charges connectées aux antennes d'un réseau. La quantification précise et l'illustration des effets de couplage au sein de réseaux finis linéaires et deux dimensions, d'antennes à large bande et a bipolarisation. L'avantage essentiel des méthodes de modélisation globale est qu'elles ne nécessitent pas a priori la connaissance de la solution au problème pose. Cependant, il est important de rappeler que cette modélisation profite largement de l'expérimentation et du savoir-faire acquis antérieurement et que la confrontation avec l'expérience est de rigueur. Aujourd'hui la fiabilité de l'outil permet d'optimiser des structures complexes et de s'affranchir d'une expérimentation complète trop couteuse. Toutes les antennes présentées dans ce mémoire ont été réalisées et testées au laboratoire antennes et réseaux ura 834 cnrs de l'université de rennes I
Apport des surfaces à haute impédance pour la conception d'antennes réseaux compactes et d'antennes réseaux à très large bande passante by Fabrice Linot( Book )

2 editions published in 2011 in French and held by 2 WorldCat member libraries worldwide

Phased array antennas play a growing place in modern airborne systems because it offers radio electric performances and integration capacities which can't be considered with others technologies. These applications can be grouped within the same system including antenna arrays with scan angle over a large frequency spectrum. Nevertheless, important antenna performance limitations are due to mutual coupling between radiating elements and to limited space available for antenna integration into aircraft. These two limitations can be removed with High Impedance Surface. HIS behaves as an artificial magnetic conductor (AMC) and/or electromagnetic band gap material which exhibits forbidden electromagnetic band gap (EBG) for surface waves at certain frequency bandwidths. After a state of the art of artificial materials and their abilities to reduce mutual coupling in an array, we present and propose analytical and numerical methods, validated by measurements, to design AMC, EBG structures, and compact absorbing material. Then we study several configurations employing classical solutions and HIS solutions used as a filter to reduce mutual coupling between two microstrip antennas spaced by a half wavelength. Finally, we present an analytical method, validated by numerical simulations, for designing a self-complementary connected antenna array located above a high impedance ground plane. Employed as reflector, HIS can create several additional bandwidths, possibly agile in frequency, and then widening the initial bandwidth of the antenna array. Moreover HIS can be designed for reducing the total antenna thickness
Conception et réalisation d'un sondeur de canal multi-capteur utilisant les corrélateurs cinq-ports pour la mesure de propagation à l'intérieur des bâtiments by Văn Yem Vũ( Book )

2 editions published in 2005 in French and held by 2 WorldCat member libraries worldwide

The five-port correlator in microstrip technology consists of a ring with 5 arms and three diode power detectors. The ratio of two waves (Radio Frequency and Local Oscillator) is determined as a linear combination of the power levels measured at the five -port's outputs. Advantages of using five-port are its low-cost, its less sensibility to phase and amplitude imbalances and its operation in a wide frequency band. We propose a spatio-temporal channel sounder that consists of an 8 quasi-Yagi antenna elements and of 8 five-ports at reception The channel sounder designed for indoor propagation measurements follows us to measure time delay (TOA: Time Of Arrival) and Direction Of Arrival (DOA) in azimuth and in elevation of multi-path signals simultaneously. The DOA is estimated by measuring the phase difference of signals picked up by an antenna array and the estimation of TOA is based on the phase difference measured at two successive frequencies in the band from 2.3 GHz to 2.5 GHz with frequency step of 4 MHz at one five-port. The high resolution algorithm MUSIC (Multiple Signal Classification) associated with spatial smoothing pre-processing is used for TOA and DOA estimation. The simulation and measurement results show that we can estimate a number of signals bigger than the number of antenna elements. The proposed channel sounder has a low-cost and the measurement is performed simultaneously
Low-profile metamaterial-based L-band antennas by Shah Nawaz Burokur( )

1 edition published in 2016 in English and held by 2 WorldCat member libraries worldwide

Étude conjointe antenne-canal pour les communications ultra large bande en présence du corps humain by Hassan Ghannoum( Book )

2 editions published in 2006 in French and held by 2 WorldCat member libraries worldwide

L'Ultra Large Bande est une technique de transmission radio qui consiste à utiliser des signaux dont le spectre s'étale sur une large bande de fréquences, typiquement de l'ordre de 500 MHz à plusieurs GHz. Elle fut d'abord utilisée pour des applications radars puis transposée aux applications de télécommunications, suscitant ainsi un intérêt grandissant au sein de la communauté académique et industrielle. Les principales caractéristiques de cette technologie lui confèrent le statut d'un candidat prometteur pour les systèmes de communications radio haut-débit à courte portée. Cette thèse poursuit un objectif double. Le premier consiste à améliorer l'analyse de performances des antennes ULB et à en proposer de nouvelles structures soit pour la mesure de canal, soit pour les communications. Dans cet objectif, des descripteurs temporels particulièrement pertinents pour le mode impulsionnel sont introduits et appliqués aux antennes réalisées. Le deuxième objectif de cette thèse est de caractériser les réseaux ULB corporels. Dans ce contexte, la question de l'interaction antenne ULB/corps s'est naturellement posée. De nombreuses simulations et mesures sur des personnes volontaires ont permis d'étudier cette question. Une campagne extensive de mesures du canal ULB sur le corps a été ensuite réalisée, ce qui a permis de proposer un modèle statistique capable de reproduire les effets de ce canal de manière réaliste, en configuration statique
Authentification d'etiquettes RFID sans puce par des approches RF non intrusives by Zeshan Ali( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

In this thesis, the concept of chipless radio frequency identification (RFID) is extended to the chipless authentication where each tag has to present a unique signature that can never be reproduced even if someone tries to copy the tag. For this purpose, natural randomness (i.e., inherent in the fabrication process) along dimension parameters of resonators is utilized. Such natural randomness can produce unique electromagnetic (EM) signatures that are possibly employed for authentication. Initially, we proved the proposed idea by purposely applying the dimensional variations along the resonators. Different values of the purposely applied dimensional variations are used to find the minimum detectable variation by the chipless RFID radar approach. Additionally, a statistical analysis has been performed to calculate the error rates. Subsequently, a spectrogram approach is proposed to extract aspect-independent parameters (i.e., the frequency of resonance and quality factor) of chipless RFID tags. Finally, we fabricated numerous resonators exhibiting natural randomness (without any purposely applied dimensional variations) to characterize the potential of the chipless tags for authentication applications. Low-cost realization technologies such as printed circuit board (PCB) using chemical etching process and inkjet printing using ordinary office printer are utilized. The natural randomness along the dimensions of resonators is also confirmed by the microscopic analysis using a digital microscope
Mobile phone model with metamaterials to reduce the exposure by Yenny Pinto( )

1 edition published in 2016 in English and held by 2 WorldCat member libraries worldwide

Conception d'antennes compactes ultra large bande bipolarisation by Mohammad Vahdani( Book )

2 editions published in 2008 in English and held by 2 WorldCat member libraries worldwide

L'objectif principal de cette thèse est de concevoir et d'analyser des antennes associées à des systèmes d'alimentations compacts à bande passante voisine ou supérieure à l'octave et à double polarisation. Cette étude a été effectuée au département COMELEC de TELECOM ParisTech sous la direction de Xavier Begaud. Aujourd'hui dans les systèmes télécommunication sans fil, il y a trois demandes croissantes: Premièrement on a besoin d'émetteurs/récepteurs large bande pour augmenter le débit d'information. Deuxièmement pour des raisons d'esthétique et portabilité, il est nécessaire de concevoir des antennes très compactes et de faible-encombrement. Enfin dans les systèmes télécommunications sans fil notamment, les antennes de stations de base avec deux polarisations orthogonales peuvent aussi permettre d'augmenter la performance des systèmes. On a besoin de systèmes d'alimentations avec ces trois caractéristiques : ultra-large bande, double polarisation et faible encombrement. Afin de valider les performances de ces systèmes d'alimentations, des antennes avec des caractéristiques compatibles ont été étudiées. Durant le déroulement de la thèse, on a parcouru les étapes suivantes : dans la première étape, un système d'alimentation ultra large bande à simple polarisation 3D a été réalisé. Dans la deuxième étape nous l'avons fait évoluer vers une structure à double polarisation. Finalement, une configuration intégrée à double polarisation a été conçue et réalisée. Cette dernière partie est le cœur de mon travail et les parties précédentes ont été conduites pour aboutir à cette configuration intégrée. Il faut noter que dans ce travail, l'expression "large bande ou ultra large bande (ULB ou UWB : Ultra Wide Band)" se réfère à une bande de fréquence voisine ou supérieure à une octave pour un module du coefficient réflexion inférieur à -10 dB
Conception et réalisation d'un système de télécommunications MIMO avec formation numérique de faisceaux en réception : calibrage aveugle du démodulateur triphasé zéro-IF et comparaison au démodulateur classique à 2 voies I et Q by Kaïs Mabrouk( Book )

in French and held by 2 WorldCat member libraries worldwide

Within the framework of this research work, we have interested to a MIMO (Multiple Input Multiple Output) telecommunication system using the spatial multiplexing, Zero-IF receptors and the digital beamforming technique. The first part in this work is consecrated to a comparative study between two different kinds of Zero-IF demodulators: the classical IQ demodulator and the five-port and three-phase one. This study has allowed to highlight the three dimensional aspect of five-port and three-phase demodulators, to win up to 20dB in terms of rejection of inter-modulation product. Also this three dimensional aspect discovery help us to find a new blind calibration method. The second part of this thesis focuses on the prototyping of a MIMO system. This phase has allowed us to set the difficulties of the implementation of this systems kind and to highlight new problematics that don't appear beforehand in mono-transceiver system. Moreover, a beamforming algorithm was developed in this part. This digital beamfoming has permit to increase the capacity as well as the quality of link when considering the MIMO system as N parallel SIMO systems. Compared to the ZF (Zero Forcing technique), we have proved that the beamforming permit the achievement a better signal quality for lower values of the signal to noise ratio
Sondeur de canal de propagation multi-capteur appliqué à la mesure de canal de propagation pour l'Ultra Large Bande (6GHz - 8.5 GHz) à l'intérieur des bâtiments by Hajar El Arja( Book )

in English and held by 2 WorldCat member libraries worldwide

Ce manuscrit présente la conception d'un sondeur de canal de propagation en intérieur de bâtiment en contexte Ultra Large Bande ULB. Le sondeur est basé sur une architecture parallèle en réception composée de circuits cinq ports et d'un réseau d'antennes imprimées LTSA (Linear Tapered Slot Antenna). Le sondeur a été réalisé et testé dans la bande de fréquence ULB (6 to 8.5 GHz) alloué par l'ETSI . Les mesures réalisées ont permis d'étudier les directions d'arrivée (DOA) ainsi que le temps d'arrivée des ondes correspondantes aux multi trajets à l'intérieur d'un bâtiment. L'association de la technique cinq-port et de la méthode d'estimation MUSIC (Multiple Signal Classification) permet d'avoir un sondeur à faible coût de réalisation et à haute précision d'estimation. Plusieurs scénarios de propagation sont traités dans le manuscrit que se soit en condition de visibilité (LOS) ou de non visibilité (NLOS)
Low profile superstrate using transformation optics for semicircular radiation pattern of antenna by Chetan Joshi( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

Miniaturisation des antennes large bande à l'aide de matériaux artificiels by Michaël Grelier( Book )

in French and held by 2 WorldCat member libraries worldwide

In the field of electronic warfare, control of the electromagnetic spectrum is essential. Antennas must have an extremely broad frequency coverage. Their frequency band of operation may exceed the decade, i.e. a ratio of 10 between high and low frequencies. In addition, the low frequency can be close to a hundred MHz thereby increasing the size of the antenna in the direction of thickness. The integration of low-band antenna is a major challenge. Frequency independent antennas loaded by a cavity absorbent are conventional antennas dedicated to electronic warfare commonly used. The work presented in this manuscript are intended to remove the absorbent present in antennas to increase efficiency and reduce their thickness. Our research was oriented towards artificial materials, such as artificial magnetic conductor (amc) and electromagnetic band gap materials (ebg), enabling the practical realization of magnetic reflector. After a state of the art of analytical, numerical and experimental methods, we study the behavior of an archimedean spiral antenna in free space and then with two types of theoretical reflectors: perfect electric conductor (pec) and perfect magnetic conductor (pmc). We proposed and experimentally validated an innovative methodology to design a wideband and low profile antenna. Finally, we presented a hybrid reflector composed of electrical and magnetic conductors. These two types of conductors are combined to extend the operating bandwidth of the antenna. Using an archimedean spiral, we show that antenna have exploitable properties at low and high frequency
Analyse et optimisation d'antennes tridimensionnelles : application à la conception d'antennes compactes intégrées dans un système de communication ultra-large bande by Anne Claire Lepage( Book )

2 editions published in 2007 in French and held by 2 WorldCat member libraries worldwide

The ever growing need for high rate wireless communication links implies to have equipments with high performance antennas, which will have to work over multifrequency bands or over a broad band. But they will also have to be integrated into radio systems, which requires the conception of compact structures without issues of electromagnetic compatibility with surrounding electronic circuits. We focused our research on three-dimensional antennas that offer numerous degrees of freedom, but this kind of structure is complex due to numerous parameters. To better understand their functioning, we developed a design process for these antennas. We begin with a study of a canonical antenna : a dipole placed near or inside an open rectangular metallic cavity. The effects of different parameters are studied to build a design method to optimise the impedance bandwidth and radiation pattern. Then, we design a three-dimensional, compact, broadband and directive antenna with a stable radiation pattern over frequency called "F-probe with triangular patch antenna". After, we proceed to a complete study of the influence of the parameters on the input impedance. This enables us to devise a simple, quick, efficient and general method to determine the impedance of this complex antenna. Thus, the "F-probe with triangular patch antenna" is optimised and reaches a -10 dB impedance bandwidth from 3.1 to 6.1 GHz. A time-domain characterisation is also proposed to determine the behaviour of the antenna in a UWB communication link. Finally, the "F-probe with triangular patch antenna" is placed into a cavity to study the influence of the integration in the radio system on the antenna's features
Miniaturisation des antennes large bande à l'aide de matériaux artificiels by Michaël Grelier( )

in French and held by 1 WorldCat member library worldwide

In the field of electronic warfare, control of the electromagnetic spectrum is essential. Antennas must have an extremely broad frequency coverage. Their frequency band of operation may exceed the decade, i.e. a ratio of 10 between high and low frequencies. In addition, the low frequency can be close to a hundred MHz thereby increasing the size of the antenna in the direction of thickness. The integration of low-band antenna is a major challenge. Frequency independent antennas loaded by a cavity absorbent are conventional antennas dedicated to electronic warfare commonly used. The work presented in this manuscript are intended to remove the absorbent present in antennas to increase efficiency and reduce their thickness. Our research was oriented towards artificial materials, such as artificial magnetic conductor (amc) and electromagnetic band gap materials (ebg), enabling the practical realization of magnetic reflector. After a state of the art of analytical, numerical and experimental methods, we study the behavior of an archimedean spiral antenna in free space and then with two types of theoretical reflectors: perfect electric conductor (pec) and perfect magnetic conductor (pmc). We proposed and experimentally validated an innovative methodology to design a wideband and low profile antenna. Finally, we presented a hybrid reflector composed of electrical and magnetic conductors. These two types of conductors are combined to extend the operating bandwidth of the antenna. Using an archimedean spiral, we show that antenna have exploitable properties at low and high frequency
Étude et conception d'antennes miniatures et directives à polarisation circulaire pour lecteurs RFID UHF by Sylvain Pflaum( )

1 edition published in 2013 in French and held by 1 WorldCat member library worldwide

RFID technology is now a part of our daily lives. The corresponding applications are more and more numerous and widespread. This work having been done in the framework of the PACID textile project, this thesis has the ambition to research innovative solutions for RFID readers in order to enhance the management, the traceability and the security of the industrial and commercial textiles.Towards this end, the antenna reader has to be miniature while being low-cost, directive and in circular polarization in the RFID UHF band (0.865-0.868 GHz). The two main technological challenges that we have faced for the reader antenna is managing its main direction of propagation to restrict and control the reading zone as well as the miniaturization of its size in order to easily integrate it into any environment. To respond to this problem, the research areas discussed in this manuscript were: The obtaining of the circular polarization using short-circuited resonators. The study and design of microstrip antennas based on EBG (Electromagnetic Band Gap). Type metamaterials to improve their directivity by using the original properties of these structures. The research of new miniaturization techniques for printed antennas by introducing a new EBG ground plane
Réseaux de capteurs sans fil enfouis ultra large bande : antenne et liens radios by Hamadache Zemmour( )

1 edition published in 2016 in French and held by 1 WorldCat member library worldwide

Wireless underground sensor networks (WUSN) consist of sensors which are buried in a medium with their antennas, in particular in soil. They attract a huge interest in different fields, like environment monitoring, precise agriculture, navigation and security. The existing narrowband systems operate at frequencies below 1 GHz. These systems imply the use of cumbersome antennas, which complicates the deployment and increases its cost. Furthermore, the use of narrow bandwidths limits the possible communication data rates and the potential resolution in localization applications. Finally, current systems are very energy consuming, which limits the lifetime of the underground elements.To overcome these drawbacks for certain applications of WUSN, we propose in this thesis the use of ultra wideband technology (UWB), in the normalized band 3.1 - 10.6 GHz, in WUSN. This technique allows the use of compact antennas, simplifying deployment, improving the localization accuracy and increasing communication data rates and the lifetime of the underground sensors.In order to assess the feasibility study of UWB WUSN, we have designed and realized three compact UWB antennas and analyzed the effect of soil on the performances of these underground UWB antennas and on the underground UWB communication links. Compared with operating in free space, burying the antenna shifts the antenna bandwidth towards low frequencies. This shift increases with soil water content. The attenuation introduced by the buried UWB channel, increases with the operating frequency, the burial depth and the soil moisture. However, we have shown that reliable communications are possible for distances of propagation in soil smaller than 30 cm and soil water contents below 20%
 
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Ultra-wide band antennas
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Alternative Names
Xavier Begaud investigador

Xavier Begaud wetenschapper

Languages
English (24)

French (21)